Aminosulfonylphenyl-azo-indolyl dyestuffs

ABSTRACT

Monoazo dyestuffs which in the form of the free acid correspond to the general formula ##STR1## wherein R 0 , R 1 , R 2 , R 3 , R 4 , R 5 , R 6  and R 7  have the meaning given in the description and their use for the dyeing of natural and synthetic fibre materials, especially for dyeing polyamide fibres. Dyeings obtained distinguish themselves by very good fastness to light. Dyestuffs are absorbed well on polyamide fibres already in a neutral to weakly acid dye bath. By polyamide fibres there are here especially understood those from synthetic polyamides such as Ε-polycaprolactam, or condensation products of adipic acid and hexamethylenediamine.

This is a continuation-in-part of pending application Ser. No. 324,606 filed Jan. 18, 1973, now abandoned.

The subject of the present invention are monoazo dyestuffs which in the form of the free acid correspond to the formula ##STR2## in which R_(o) denotes hydrogen, alkyl, aryl, aralkyl or a heterocyclic radical,

R₁ denotes hydrogen, alkyl, aralkyl or, together with R_(o) and the N atom, a 5-membered or 6-membered ring,

R₂ denotes halogen, alkyl, aralkyl, alkoxy, nitro, nitrile, carbonamide or carboxylic acid ester,

R₃ denotes halogen, alkyl or alkoxy,

R₄ denotes hydrogen or halogen,

R₅ denotes alkyl or aryl,

R₆ denotes hydrogen or alkyl and

R₇ denotes hydrogen, halogen, alkyl or alkoxy.

The alkyl groups preferably contain 1-8 C atoms and can possess further non-ionic substituents, for example hydroxyl groups, chlorine, bromine, nitrile, alkoxy or alkoxycarbonyl, especially C₁ -C₄ -alkoxy or alkoxycarbonyl.

Suitable alkyl groups R₂, R₃, R₅ and R₇ are especially unsubstituted C₁ -C₄ -alkyl radicals, such as CH₃, C₂ H₅, i-C₃ H₇, n-C₄ H₉ and i-C₄ H₉.

Suitable alkyl groups R_(o) and R₁ are in particular C₁ -C₆ -alkyl radicals, for example, CH₃, C₂ H₅, n- and iso-C₃ H₇, and n-, sec.- and iso-C₄ H₉, which can be further substituted by nonionic substituents, for example by hydroxyl groups, chlorine, bromine, organo, alkoxy, especially C₁ -C₄ -alkoxy, and alkoxycarbonyl, especially C₁ -C₄ -alkoxycarbonyl. Further alkyl groups R_(o) and R₁ are cycloalkyl groups, for example cyclohexyl.

Suitable alkyl radicals R₆ are in particular those with 1-4 C atoms which can be further substituted, for example by -CN, -CONH₂ or -COOH, such as, for example, -CH₃, -C₂ H₅, -C₃ H₇, -C₄ H₉, -C₂ H₄ CN, -C₂ H₄ CONH₂ and -C₂ H₄ COOH.

Suitable alkoxy radicals R₂, R₃ and R₇ are in particular those with 1-4 C atoms, for example -OCH₃, -OC₂ H₅, -OC₃ H₇ and OC₄ H₉.

Suitable aryl radicals R₅ are in particular phenyl or naphthyl radicals which are optionally substituted further, for example by alkyl, especially C₁ -C₄ -alkyl, alkoxy, especially C₁ -C₄ -alkoxy, or halogen, especially chlorine or bromine, such as phenyl, biphenylyl or naphthyl.

Suitable aryl radicals R_(o) are in particular phenyl or naphthyl radicals which are optionally substituted further, e.g. tolyl.

Suitable aralkyl radicals R_(o) and R₁ are in particular benzyl or phenylethyl groups which are optionally substituted further by non-ionic substituents.

An example of a suitable heterocyclic radical R_(o) is the 3-sulpholanyl radical.

Examples of suitable rings R_(o) + R₁ including the N-atom are: ##STR3##

Suitable halogen atoms R₂, R₃, R₄ and R₇ are fluorine, chlorine and bromine.

Within the framework of the formula (I), preferred dyestuffs are those which in the form of the free acid correspond to the formula ##STR4## wherein R_(o), R₁, R₂, R₃, R₅, R₆ and R₇ have the abovementioned meaning.

Particularly preferred dyestuffs are those which in the form of the free acid correspond to the formula ##STR5## wherein R_(o), R₁, R₅ and R₆ have the abovementioned meaning,

R₂ ' and R₃ ' represent chlorine or bromine and

R₇ ' represents hydrogen, chlorine or C₁ -C₄ -alkyl which is not substituted further,

especially those which in the form of the free acid correspond to the formula ##STR6## wherein R_(o), R₁, R₂ ', R₃ ' and R₇ ' have the abovementioned meaning,

R₅ ' denotes C₁ -C₄ -alkyl which is not substituted further, or phenyl and

R₆ ' denotes hydrogen or C₁ -C₄ -alkyl which is optionally substituted by cyano, carbonamide or carboxyl.

Included within the scope of this invention is the class of dyestuffs having the formula (I) in which

R_(o) denotes hydrogen; C₁ -C₆ -alkyl; C₁ -C₆ -alkyl substituted by hydroxy, chlorine, bromine, cyano, C₁ -C₄ -alkoxy or C₁ -C₄ -alkoxycarbonyl; cyclohexyl; phenyl; naphthyl; tolyl; benzyl; phenethyl; 3-sulfolanyl;

R₁ denotes hydrogen; C₁ -C₆ -alkyl; C₁ -C₆ -alkyl substituted by hydroxy, chlorine, bromine, cyano, C₁ -C₄ -alkoxy or C₁ -C₄ -alkoxycarbonyl; cyclohexyl or together with R_(o) a piperidino, pyrrolidino or morpholino ring;

R₂ and R₃ denote chlorine or bromine

R₄ denotes hydrogen and

R₅ denotes C₁ -C₄ -alkyl, phenyl, naphthyl or biphenylyl,

R₆ denotes hydrogen; C₁ -C₄ -alkyl, C₁ -C₄ -alkyl substituted by cyano, carbonamide or carboxy

R₇ denotes hydrogen, chlorine or C₁ -C₄ -alkyl.

The new dyestuffs of the formula (I) are obtained if amines of the general formula ##STR7## wherein

R_(o), R₁, R₂, R₃ and R₄ have the abovementioned meaning are diazotised and combined with coupling components of the general formula ##STR8## wherein

R₅, R₆ and R₇ have the abovementioned meaning.

The diazo components of the general formula (V) are either known from the literature or are obtained in accordance with instructions known from the literature, for example by amidising acetylaminobenzenesulphochlorides or nitrobenzenesulphochlorides with amines of the formula ##STR9## wherein

R_(o) and R₁ have the abovementioned meaning and splitting of the acetyl group or converting the nitro group into the amino group by reduction.

Examples of suitable amines of the formula (V) are: aniline-4,5-dichloro-2-N,N-dimethyl-sulphonamide, aniline-4,5-dichloro-2-N,N-diethyl-sulphonamide, aniline-4,5-dichloro-2-N-ethyl-sulphonamide, aniline-2,5-dichloro-4-sulphonamide, aniline-2,5-dichloro-4-N-methyl-sulphonamide, aniline-2,5-dichloro-4-N-ethyl-sulphonamide, aniline-2,5-dichloro-4-N-propyl-sulphonamide, aniline-2,5-dichloro-4-N-butyl-sulphonamide, aniline-2,5-dichloro-4-N-benzyl-sulphonamide, aniline-2,5-dichloro-4-N-phenyl-sulphonamide, aniline-2,5-dichloro-4-N-(m-tolyl)-sulphonamide, aniline-2,5-dichloro-4-N-γ-chloropropyl-sulphonamide, aniline-2,5-dichloro-4-β-hydroxyethyl-sulphonamide, aniline-2,5-dichloro-4-N-γ-hydroxypropyl-sulphonamide, aniline-2,5-dichloro-4-N-γ-hydroxybutyl-sulphonamide, aniline-2,5-dichloro-4-N-cyclohexyl-sulphonamide, aniline-2,5-dichloro-4-N,N-dimethyl-sulphonamide, aniline-2,5-dichloro-4-N,N-diethyl-sulphonamide, aniline-2,5-dichloro-4-N,N-bis-(β-hydroxyethyl)-sulphonamide, aniline-2,5-dichloro-4-N,N-tetramethylene-sulphonamide, aniline-2,5-dichloro-4-N,N-pentamethylene-sulphonamide, aniline-2,6-dichloro-4-sulphonamide, aniline-2,6-dichloro-4-N-methyl-sulphonamide, aniline-2,6-dichloro-4-N-ethyl-sulphonamide, aniline-2,6-dichloro-4-N-β-hydroxyethyl-sulphonamide, aniline-2,6-dichloro-4-N-benzyl-sulphonamide, aniline-2,6-dichloro-4-N-phenyl-sulphonamide, aniline-2,6-dichloro-4-N-γ-hydroxybutyl-sulphonamide, aniline-2,6-dichloro-4-N,N-diethyl-sulphonamide, aniline-2,6-dichloro-4-N-methyl-N-phenyl-sulphonamide, aniline-2,6-dichloro-4-N-methyl-N-β-hydroxyethyl-sulphonamide, aniline-2,6-dichloro-4-N,N-pentamethylenesulphonamide, aniline-2,6-dichloro-4-N,N-bis-(β-hydroxyethyl)-sulphonamide, aniline-2-chloro-5-bromo-4-N,N-dimethyl-sulphonamide, aniline-2-chloro-5-bromo-4-N-ethyl-sulphonamide, aniline-2-chloro-5-bromo-4-N-benzyl-sulphonamide, aniline-2-chloro-5-bromo-4-N,N-bis-(β-hydroxyethyl)-sulphonamide, aniline-2-chloro-5-bromo-4-N-cyclohexyl-sulphonamide, aniline-2-chloro-5-bromo-4-N,N-dipropylsulphonamide, aniline-2-bromo-5-chloro-4-N,N-dimethyl-sulphonamide, aniline-2-bromo-5-chloro-4-N-γ-hydroxypropyl-sulphonamide, aniline-2-bromo-5-chloro-4-N-ethyl-sulphonamide, aniline-2-chloro-6-bromo-4-N-methyl-sulphonamide, aniline-2-chloro-6-bromo-4-N,N-diethyl-sulphonamide, aniline-2-chloro-6-bromo-4-N-phenyl-sulphonamide, aniline-2,5-dibromo-4-N-benzyl-sulphonamide, aniline-2,5-dibromo-4-N,N-diethyl-sulphonamide, aniline-2,5-dibromo-4-N,N-pentamethylene-sulphonamide, aniline-2,5-dibromo-4-N-methyl-N-β-hydroxy-ethyl-sulphonamide, aniline-2,6-dibromo-4-N,N-dimethyl-sulphonamide, aniline-2,6-dibromo-4-N-β-hydroxyethyl-sulphonamide, aniline-2,6-dibromo-4-N-propyl-sulphonamide, aniline-2,6-dibromo-4-N-butyl-sulphonamide, aniline-2-chloro-6-methyl-4-N-methyl-sulphonamide, aniline-2-chloro-6-methyl-4-sulphonamide, aniline-2-chloro-6-methyl-4-N,N-diethyl-sulphonamide, aniline-4-chloro-6-methyl-2-N,N-diethyl-sulphonamide, aniline-4-chloro-6-methyl-2-N-β-hydroxyethylsulphonamide, aniline-4-chloro-6-methyl-2-N,N-dimethyl-sulphonamide, aniline-4-chloro-5-methyl-2-N,N-diethyl-sulphonamide, aniline-4-chloro-5-methyl-2-N,N-dimethyl-sulphonamide, aniline-2,6-dimethyl-3-sulphonamide, aniline-2,6-dimethyl-3-N-methyl-sulphonamide, aniline-2,6-dimethyl-3-N,N-diethyl-sulphonamide, aniline-2,5,6-trichloro-3-sulphonamide, aniline-2,5,6-trichloro-3-N-methyl-sulphonamide, aniline-2,5,6-trichloro-3-N-methyl-N-β-hydroxy-ethyl-sulphonamide, aniline-2,5,6-trichloro-N,N-diethyl-sulphonamide, aniline-4,6-dichloro-2-N,N-dimethyl-sulphonamide, aniline-4,6-dichloro-2-N-methyl-sulphonamide, aniline-4,6-dichloro-2-N,N-dimethylsulphonamide, aniline-2,4-dimethyl-5-N,N-dimethyl-sulphonamide, aniline-2,4-dimethyl-5-N-ethyl-sulphonamide, aniline-2,4-dimethyl-5-N-γ-hydroxybutyl-sulphonamide, aniline-4,5-dichloro-4-N-methyl-sulphonamide, aniline-4,5-dichloro-4-γ-hydroxybutylsulphonamide, aniline-4,5-dichloro-4-N-benzyl-sulphonamide, aniline-2,5-dichloro-N-methoxyethyl-sulphonamide, N-(2,5-dichloro-4-amino-phenyl-sulphonyl)-morpholine, N-(2,5-dichloro-4-amino-phenyl-sulphonyl)-piperidine, aniline-2,5-dichloro-4-N-sulpholanyl-(3)-sulphonamide, and aniline-2,5-dichloro-4-N-methyl-N-sulpholanyl-(3)-sulphonamide.

Examples of suitable coupling components of the formula (VI) are the indolesulphonic acids described in German Patent Specification No. 137,117 and other indolesulphonic acids which are obtained analogously to the processes described in German Patent Specification No. 137,117 by sulphonation of 2-alkylindoles or 2-arylindoles . This probably yields the indole-5-sulphonic acids, at least when using the indoles which are unsubstituted in the 5-position. As examples of suitable indolesulphonic acids there may be mentioned: 2-methyl-indole-sulphonic acid, 2-ethyl-indole-sulphonic acid, 2-phenyl-indole-sulphonic acid, 1-methyl-2-phenyl-indole-sulphonic acid, 1,2-dimethyl-indolesulphonic acid, 1-ethyl-2-methyl-indole-sulphonic acid, 1,2,5-trimethyl-indole-sulphonic acid and 2,5-dimethyl-indole-sulphonic acid.

The dyestuffs according to the invention are suitable for dyeing natural and synthetic fibre materials, especially for dyeing polyamide fibres. They yield level yellow to orange dyeings of good yield and very good wet fastness like fastness to washing, perspiration and hot water and fastness to light. They are absorbed well on polyamide fibres already in a neutral to weakly acid dye bath. By polyamide fibres there are here especially understood those from synthetic polyamides such as ε-polycaprolactam, or condensation products of adipic acid and hexamethylenediamine. The dyestuffs are employed in the form of the free acid or in the form of their salts, especially of the alkali metal salts such as the sodium salts or potassium salts or of the ammonium salts. The formulae given above are those of the free acid.

EXAMPLE 1

5.25 g of 2,5-dichloro-aniline-sulphonamide are introduced, at 3°-5°, into a mixture of 20 ml of glacial acetic acid, 20 ml of concentrated sulphuric acid and 7.5 g of nitrosylsulphuric acid and the mixture is stirred for a further 1.5 hours at 3°-5° C. It is then poured out onto ice/H₂ O, a little amidosulphonic acid is added and the resulting solution is combined with a solution of 4.74 g of 2-methyl-indole-sulphonic acid in water. The mixture is neutralised somewhat with sodium acetate and after completion of coupling the dyestuff, which in the form of the free acid corresponds to the formula ##STR10## is isolated by salting out and filtering off. It dyes polyamide, from a weakly acid neutral bath, in yellow shades of very good fastness to light.

EXAMPLE 2

If the procedure described in Example 1 is followed but 5.85 g of 2,5-dichloro-aniline-4-N,N-dimethylsulphonamide are employed as the diazo component, a dyestuff is obtained which in the form of the free acid corresponds to the formula ##STR11## and dyes polyamide from a weakly acid or neutral bath in yellow shades of very good fastness to light.

EXAMPLE 3

6.5 g of 2,5-dichloro-aniline-4-N-methyl-N-γ-hydroxyethyl-sulphonamide are diazotised, in dilute hydrochloric acid, with 16 g of a 10% strength sodium nitrite solution at 0°. After the excess nitrite has been removed with amidosulphonic acid, a solution of 4.74 g of 2-methyl-indole-sulphonic acid in water is added and the mixture is buffered somewhat with sodium acetate. The dyestuff thus obtained corresponds, in the form of the free acid, to the formula ##STR12## and dyes polyamide from a weakly acid or neutral bath in yellow shades of very good fastness to light.

DYEING EXAMPLE

0.1 g of the dyestuff from Example 1 is dissolved in 100 ml of hot water, 5 ml of 10% strength ammonium acetate solution are added and the mixture is diluted to a volume of 500 ml with water. 10 g of polyamide fibres are introduced into the dye bath, which is brought to the boil over the course of 20 minutes, 4 ml of 10% strength acetic acid are added and the whole is kept at the boil for one hour. Thereafter the fibres are rinsed and dried at 70°-80° C. A dyeing in a yellow shade of very good fastness to light and to wet processing is obtained.

If the procedure in Example 1 or in Example 3 is followed but the compounds listed in Column II of the table which follows are employed as diazo components, valuable water-soluble dyestuffs are again obtained, which dye polyamide, from a weakly acid or neutral bath, in yellow to orange light-fast shades.

    __________________________________________________________________________     Example                                                                             Diazo component        Coupling component                                 __________________________________________________________________________      4                                                                                   ##STR13##             2-Phenyl-indole-sulphonic acid                      5   "                      1-Methyl-2-phenyl-indole-sulphonic acid             6   "                      1,2-Dimethyl-indole-sulphonic acid                  7                                                                                   ##STR14##             2-Phenyl-indole-sulphonic acid                      8   "                      1-Ethyl-2-methyl-indole-sulphonic acid              9                                                                                   ##STR15##             2-Methyl-indole-sulphonic acid                     10   "                      1-Methyl-2-phenyl-indole-sulphonic acid            11   "                      1,2,5-Trimethyl-indole-sulphonic acid              12   "                      2,5-Dimethyl-indole-sulphonic acid                 13                                                                                   ##STR16##             2-Phenyl-indole-sulphonic acid                     14   "                      2-Methyl-indole-sulphonic acid                     15                                                                                   ##STR17##             1-Methyl-2-phenyl-indole-sulphonic acid            16                                                                                   ##STR18##             2-Phenyl-indole-sulphonic acid                     17   "                      2-Methyl-indole-sulphonic acid                     18   "                      2-Ethyl-indole-sulphonic acid                      19                                                                                   ##STR19##             1-Methyl-2-phenyl-indole-sulphonic acid            20                          2,5-Dimethyl-indole-sulphonic acid                 21                                                                                   ##STR20##             2-Methyl-indole-sulphonic acid                     22                                                                                   ##STR21##             1-Methyl-2-phenyl-indole-sulphonic acid            23   "                      1,2,5-Trimethyl-indole-sulphonic acid              24                                                                                   ##STR22##             2-Methyl-indole-sulphonic acid                     25   "                      2-Phenyl-indole-sulphonic acid                     26                                                                                   ##STR23##             2-Methyl-indole-sulphonic acid                     27   "                      1-Methyl-2-phenyl-indole-sulphonic acid            28                                                                                   ##STR24##             2-Methyl-indole-sulphonic acid                     29   "                      2,5-Dimethyl-indole-sulphonic acid                 30   "                      2-Ethyl-indole-sulphonic acid                      31                                                                                   ##STR25##             2-Phenyl-indole-sulphonic acid                     32                                                                                   ##STR26##             2-Methyl-indole-sulphonic acid                     33                                                                                   ##STR27##             2-Methyl-indole-sulphonic acid                     34   "                      2-Phenyl-indole-sulphonic acid                     35                                                                                   ##STR28##             2-Ethyl-indole-sulphonic acid                      36   "                      2-Methyl-indole-sulphonic acid                     37                                                                                   ##STR29##             2-Phenyl-indole-sulphonic acid                     38   "                      1-Methyl-2-phenyl-indole-sulphonic acid            39                                                                                   ##STR30##             2-Methyl-indole-sulphonic acid                     40                                                                                   ##STR31##             1-Methyl-2-phenyl-indole-sulphonic acid            41                                                                                   ##STR32##             2-Methyl-indole-sulphonic acid                     42   "                      1-Methyl-2-phenyl-indole-sulphonic acid            43   "                      2,5-Dimethyl-indole-sulphonic acid                 44                                                                                   ##STR33##             2-Ethyl-indole-sulphonic acid                      45   "                      1-Methyl-2-phenyl-indole-sulphonic acid            46                                                                                   ##STR34##             2-Methyl-indole-sulphonic acid                     47                                                                                   ##STR35##             2-Phenyl-indole-sulphonic acid                     48                                                                                   ##STR36##             2-Methyl-indole-sulphonic acid                     49   "                      1-Methyl-2-phenyl-indole-sulphonic acid            50                                                                                   ##STR37##             2-Methyl-indole-sulphonic acid                     51   "                      2-Phenyl-indole-sulphonic acid                     52                                                                                   ##STR38##             2-Methyl-indole-sulphonic acid                     53   "                      1-Methyl-2-phenyl-indole-sulphonic acid            54                                                                                   ##STR39##             2,5-Dimethyl-indole-sulphonic acid                 55   "                      2-Ethyl-indole-sulphonic acid                      56                                                                                   ##STR40##             1,2,5-Trimethyl-indole-sulphonic acid              57   "                      1-Methyl-2-phenyl-indole-sulphonic acid            58                                                                                   ##STR41##             2-Methyl-indole-sulphonic acid                     59                                                                                   ##STR42##             2-Phenyl-indole-sulphonic acid                     60                                                                                   ##STR43##             2-Methyl-indole-sulphonic acid                     61                                                                                   ##STR44##             1-Methyl-2-phenyl-indole-sulphonic acid            62                                                                                   ##STR45##             1-Ethyl-2-methyl-indole-sulphonic acid             63   "                      2,5-Dimethyl-indole-sulphonic acid                 64                                                                                   ##STR46##             2-Methyl-indole-sulphonic acid                     65   "                      1-Methyl-2-phenyl-indole-sulphonic acid            66                                                                                   ##STR47##             2-Methyl-indole-sulphonic acid                     67   "                      1,2-Dimethyl-indole-sulphonic acid                 68                                                                                   ##STR48##             2-Methyl-indole-sulphonic acid                     69   "                      1-Methyl-2-phenyl-indole-sulphonic acid            70   "                      2-Phenyl-indole-sulphonic acid                     71                                                                                   ##STR49##             2-Methyl-indole-sulphonic acid                     72   "                      1,2-Dimethyl-indole-sulphonic acid                 73                                                                                   ##STR50##             1-Methyl-2-phenyl-indole-sulphonic acid            74   "                      1-Ethyl-2-methyl-indole-sulphonic acid             75                                                                                   ##STR51##             2-Methyl-indole-sulphonic acid                     76   "                      2,5-Dimethyl-indole-sulphonic acid                 77                                                                                   ##STR52##             1-Methyl-2-phenyl-indole-sulphonic acid            78   "                      1,2,5-Trimethyl-indole-sulphonic acid              79                                                                                   ##STR53##             2-Methyl-indole-sulphonic acid                     80                                                                                   ##STR54##             1,2-Dimethyl-indole-sulphonic acid                 81   "                      2-Phenyl-indole-sulphonic acid                     82                                                                                   ##STR55##             1-Methyl-2-phenyl-sulphonic acid                   83   "                      2-Methyl-indole-sulphonic acid                     84                                                                                   ##STR56##             2-Methyl-indole-sulphonic acid                     85   "                      1,2-Dimethyl-indole-sulphonic acid                 86   "                      2-Phenyl-indole-sulphonic acid                     87                                                                                   ##STR57##             2-Methyl-indole-sulphonic acid                     88   "                      2-Phenyl-indole-sulphonic acid                     89                                                                                   ##STR58##             2-Methyl-indole-sulphonic acid                     90   "                      2-Phenyl-indole-sulphonic acid                     91   "                      1-Methyl-2-phenyl-indole-sulphonic acid            92                                                                                   ##STR59##             1,2-Dimethyl-indole-sulphonic acid                 93   "                      2-Methyl-indole-sulphonic acid                     94                                                                                   ##STR60##             2-Phenyl-indole-sulphonic acid                     95   "                      1-Methyl-2-phenyl-indole-sulphonic acid            96                                                                                   ##STR61##             2-Phenyl-indole-sulphonic acid                     97   "                      2-Methyl-indole-sulphonic acid                     98   "                      1-Methyl-2-phenyl-indole-sulphonic acid            99   "                      2,5-Dimethyl-indole-sulphonic acid                 100                                                                                  ##STR62##             2-Methyl-indole-sulphonic acid                     101  "                      2-Phenyl-indole-sulphonic acid                     102  "                      1-Methyl-2-phenyl-indole-sulphonic                 __________________________________________________________________________                                 acid                                          

EXAMPLE 103

193 g of 2-phenyl-indole are introduced at 20°-25° C into 300 ml of sulphuric acid monohydrate and 650 g of 20% strength oleum are then allowed to run in over the course of 20 minutes, during which the temperature rises to 40° C. The mixture is stirred for a further hour at 40° C and is poured out onto 1600 g of ice, whereupon the 2-phenyl-indole-sulphonic acid precipitates. It is filtered off, washed with saturated sodium chloride solution until free of acid, and dried at 60° C. 

We claim:
 1. Monoazo dyestuff which in the form of the free acid corresponds to the formula ##STR63## wherein R_(o) denotes hydrogen; C₁ -C₆ -alkyl; C₁ -C₆ -alkyl substituted by hydroxy, chlorine, bromine, cyano, C₁ -C₄ -alkoxy or C₁ -C₄ -alkoxycarbonyl; cyclohexyl; phenyl; naphthyl; tolyl; benzyl; phenethyl; 3-sulfolanyl;R₁ denotes hydrogen; C₁ -C₆ -alkyl; C₁ -C₆ -alkyl substituted by hydroxy, chlorine, bromine, cyano, C₁ -C₄ -alkoxy or C₁ -C₄ -alkoxycarbonyl; cyclohexyl or together with R_(o) a piperidino, pyrrolidino or morpholino ring; R₂ and R₃ denote chlorine or bromine R₄ denotes hydrogen; R₅ denotes C₁ -C₄ -alkyl, phenyl, naphthyl or biphenylyl; R₆ denotes hydrogen; C₁ -C₄ -alkyl, C₁ -C₄ -alkyl substituted by cyano, carbonamide or carboxy; and R₇ denotes hydrogen, chlorine or C₁ -C₄ -alkyl.
 2. Monoazo dyestuff of claim 1 of the formula ##STR64## wherein R_(o) denotes hydrogen; C₁ -C₆ -alkyl; C₁ -C₆ -alkyl substituted by hydroxy, chlorine, bromine, cyano, C₁ -C₄ -alkoxy or C₁ -C₄ -alkoxycarbonyl; cyclohexyl; phenyl; naphthyl; tolyl; benzyl; phenethyl; 3-sulfolanyl;R₁ denotes hydrogen; C₁ -C₆ -alkyl; C₁ -C₆ -alkyl substituted by hydroxy, chlorine, bromine, cyano, C₁ -C₄ -alkoxy or C₁ -C₄ -alkoxycarbonyl; cyclohexyl or together with R_(o) a piperidino, pyrrolidino or morpholino ring; R₂ ' denotes chlorine or bromine; R₃ ' denotes chlorine or bromine; R₅ ' denotes C₁ -C₄ -alkyl or phenyl; R₆ denotes hydrogen; C₁ -C₄ -alkyl, C₁ -C₄ -alkyl substituted by cyano, carbonamide or carboxy; and R₇ ' denotes hydrogen, chlorine or C₁ -C₄ -alkyl.
 3. Monoazo dyestuff of claim 2 of the formula ##STR65## 